At 21,504 square feet, the triplex will be akin to a house in the sky. (A house with eight bedrooms, eight full bathrooms, 10 powder rooms, a billiard room, two media rooms, a library/bar, wine room, gym and spa.)

The next-biggest condo in the city is a 16,270-square-foot pad at 3 East 95th Street, according to PropertyShark. That unit sold in 2006 for $21.9 million, or $1,346 per square foot. Next on the list is a 13,063-square-foot condo at the Plaza Hotel, which sold in 2007 for just over $50 million, or $3,830 per square foot.

There are several larger townhouses, of course. According to PropertyShark, a townhouse at 14 East 72nd Street, which real estate exec Steven Croman bought in 2002 and combined with 12 East 72nd Street, is 24,018 square feet. Meanwhile, the Harkness Mansion, at 4 East 75th Street, measures 21,700 square feet and John Paulson’s townhome at 9 East 86th Street is 20,507 square feet.

Russian billionaire Roman Abramovich is also trying to build one of the city’s largest mansions on East 75th Street. He bought 11 East 75th Street and 15 East 75th Street and may be eyeing 13 East 75th Street, as TRD reported. Together, the narrow townhouses are 24,897 square feet.

Compared with other ultra-luxe penthouses, the Chetrit triplex will be markedly larger. Extell Development’s $100 million penthouse measures 10,923 square feet, and sold for $9,154 per square foot, while Macklowe Properties’ $95 million penthouse is 8,255 square feet, or $11,508 per square foot. The penthouse at the Ritz Carlton, which includes two floors marketed together for $118 million, is comprised of 15,434 square feet priced at $7,645 per square foot.

You have to know that there’s no way the 9,999 SF apartment at The Corinthian would be asking $12,000/month. That would be $14 PSF. If you look at the rental listing page, it says the unit is 1,930 SF.